Abstract: Provided is a method of producing a roadbed material from which less hexavalent chromium leaches out through use of a crushed product of a cementitious hardened body containing hexavalent chromium as a raw material. The method includes a carbonation treatment step of subjecting the crushed product of the cementitious hardened body to carbonation treatment with a carbon dioxide-containing gas having a temperature of 50° C. to 140° C. and a water content of 1.5% or more to obtain the roadbed material from which less hexavalent chromium leaches out than before the treatment. Preferably, the method includes, before the carbonation treatment step, a crushing step of crushing the cementitious hardened body to obtain a crushed product consisting of grains having a grain size of 100 mm or less at a ratio of 50 mass % or more and a grain size of 2.36 mm or less at a ratio of 1 mass % or more.

Abstract: Provided is a method of fixing a sufficient amount of carbon dioxide contained in a carbon dioxide-containing gas (e.g., a plant exhaust gas) simply, at low cost, and efficiently. The method of fixing carbon dioxide includes a contact step of bringing a carbon dioxide-containing gas into contact with powdery or grainy particles, which are each formed of a cementitious hardened body and each have a particle size of 40 mm or less, at a temperature of from 75° C. to 110° C. to fix carbon dioxide contained in the carbon dioxide-containing gas to the powdery or grainy particles, wherein the relative humidity of the carbon dioxide-containing gas is adjusted in accordance with the particle size of the powdery or grainy particles and the state of adjustment of moisture content of the powdery or grainy particles before the contact step.

Abstract: A binder composition for immobilizing a toxic-containing material. This composition has excellent strength developing properties at low temperature and is capable of solidifying soil to suppress the elution of toxic materials from the soil.

Abstract: Provided is a method of fixing a sufficient amount of carbon dioxide contained in a carbon dioxide-containing gas (e.g., a plant exhaust gas) simply, at low cost, and efficiently. The method of fixing carbon dioxide includes a contact step of bringing a carbon dioxide-containing gas into contact with powdery or grainy particles, which are each formed of a cementitious hardened body and each have a particle size of 40 mm or less, at a temperature of from 75° C. to 110° C. to fix carbon dioxide contained in the carbon dioxide-containing gas to the powdery or grainy particles, wherein the relative humidity of the carbon dioxide-containing gas is adjusted in accordance with the particle size of the powdery or grainy particles and the state of adjustment of moisture content of the powdery or grainy particles before the contact step.